Offset measuring mechanism and offset measuring method in a bonding apparatus

ABSTRACT

An offset measuring mechanism and method used in a bonding apparatus, in which the object plane of a position detection camera is set on a hypothetical bonding working plane, and the image of imaging elements within the imaging plane is projected onto a bonding working plane. Furthermore, the tip end of a bonding tool is aligned with the bonding working plane. The object plane of the offset measuring camera is set on the bonding working plane, and the image on the bonding working plane is projected onto the imaging elements of the imaging plane of the offset measuring camera. The imaging elements detect the projected image of the imaging elements of the position detection camera or the image of the tip end of the bonding tool and output this data to the image position measuring part or tool position measuring section of the control block.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an offset measuring mechanism and anoffset measuring method in a bonding apparatus and more particularly toan offset measuring mechanism and offset measuring method for measuringthe offset between the position detection camera and bonding tool in abonding apparatus.

2. Prior Art

In a wire bonding apparatus in which, for instance, a semiconductordevice and a circuit board are connected by a fine wire, the bondingpositions on the semiconductor device are detected by a positiondetection camera, and bonding work is performed by moving the bondingtool to these positions. In this case, if the bonding tool is disposedso that the axial center of the bonding tool coincides with the opticalaxis of the position detection camera, the visual field of positiondetection is blocked; ordinarily, therefore, the position detectioncamera and the bonding tool are disposed with a specified distance inbetween. This specified distance between the optical axis of theposition detection camera and the axial center of the bonding tool iscalled an “offset”, and is an important quantity which serves as areference for positioning in the bonding work. However, this offsetvaries from instant to instant as a result of changes over time in theamount of radiant heat from the high-temperature bonding stage and theamount of heat generated in the optical system, etc., or in the amountof wear in the moving parts used for bonding, etc.

Japanese Patent No. 2982000 (Japanese Patent Application Laid-Open(Kokai) No. 2000-21923) discloses a method that determines the accurateamount of offset by a reference member, which is fixed with respect tothe bonding apparatus, and an offset correction camera, which observesthis reference member. More specifically, the optical axis of theposition detection camera is first moved to a point above the referencemember, and the relative positions of the reference member and positiondetection camera are measured. Next, the bonding tool is moved to apoint above the reference member in accordance with a specified amountof offset, and the relative positions of the reference member and thebonding tool are measured by the offset correction camera. Then, theaccurate amount of offset is determined by correcting the amount ofoffset on the bases of these measurement results.

On the other hand, Japanese Patent Application Laid-Open (Kokai) No.2001-203234 discloses a method that makes it possible to measure therelative positions of a reference member and the bonding tool by meansof a position detection camera, without using an offset correctioncamera. More specifically, instead of an offset correction camera, anoptical system is constructed by optical elements such as laser diodes,half-mirrors and prisms, etc., and image light of the reference memberand bonding tool is conducted to the position detection camera, and thenthe relative positions of the reference member and boding tool aremeasured by the position detection camera.

In the offset correction methods of the above-described prior arts, areference member is provided, and the position of the position detectioncamera and the position of the bonding tool are respectively measuredusing the reference member as a reference, and the amount of offset isdetermined based upon these measurement results. Accordingly, thereference member is fixed in a reference position outside the positiondetection camera or offset correcting camera; and thus contamination ofthe reference member occurs. Furthermore, in order to obtain accuratemeasurements of the relative positions of the reference member andbonding tool, images of both the tip end of the bonding tool and thereference member must be clearly measured. Accordingly, the bonding toolmust be caused to approach the reference member as closely as possible;and there is a danger that the bonding tool may collide with rereference member during this approach operation, thus damaging thereference member.

As seen from the above, in the prior art offset measuring methods, sincethe reference member used as a reference for position measurement isexposed to the outside, contamination and damage, etc. would occur inthe reference member, and thus it is difficult to perform periodicoffset measurements in a stable fashion.

Furthermore, since caution is required in the handling of the referencemember, which is exposed to the outside, the degree of freedom regardingthe disposition of the respective constituent elements of the bondingapparatus is limited.

SUMMARY OF THE INVENTION

Accordingly, the present invention is to solve the above-describedproblems encountered in the prior art.

The object of the present invention is to provide an offset measuringmechanism and offset measuring method in a bonding apparatus that makeis possible to perform offset measurements in a stable fashion over along period of time.

The above object is accomplished by a unique structure of the presentinvention for an offset measuring mechanism for measuring offset in abonding apparatus that includes:

-   -   a position detection camera that detects the position of a part        to be bonded on a bonding working plane,    -   a bonding tool that is disposed with an offset from the position        detection camera, and    -   a moving means for moving the position detection camera and the        bonding tool as an integral unit on a plane parallel to the        bonding working plane; and    -   in the present invention, the offset measuring mechanism that        measures the above-described offset comprises:    -   an offset measuring camera which is disposed on an opposite side        of the bonding working plane from the position detection camera        and the bonding tool and which faces the bonding working plane,    -   an imaging position measuring means which uses the moving means        to move the position detection camera into a measurement range        of the offset measuring camera and which determines a reference        position of an imaging range in an imaging plane of the position        detection camera based upon measurement of the imaging plane of        the position detection camera by the offset measuring camera,    -   a tool position measuring means which uses the moving means to        move the bonding tool into the measurement range of the offset        measuring camera and which measures a tool position of the        bonding tool with the offset measuring camera, and    -   an offset calculating means which calculates the offset based        upon a measured value of the determined reference position of        the imaging range and a measured value of the tool position.

In this structure, a reference position of the imaging range in theimaging plane of the position detection camera is determined based uponthe measurement of the imaging plane of the position detection camera bythe offset measuring camera, the tool position of the bonding tool ismeasured by the offset measuring camera, and the offset is calculatedbased upon these measured values. In other words, since the offsetmeasuring camera is fixed with respect to the bonding apparatus, themeasurement reference axes and measurement reference origin of thiscamera can be used as references.

Accordingly, by way of measuring, for instance, a reference position ofthe imaging range of the position detection camera with respect to themeasurement plane, e.g., the reference point of the imaging plane, ofthe offset measuring camera and by measuring the tool position of thebonding tool, then the offset can be determined based upon thesemeasurement results. Thus, the offset is calculated without using areference member that is exposed to the outside and is thus in a dangerof contamination or damage; and offset measurements can be performed ina stable fashion over a long period of time.

In the above structure, it is preferable that the position detectioncamera has a plurality of imaging elements disposed in two dimensions inthe directions of mutually perpendicular element disposition axes whichare associated with mutually perpendicular imaging reference axes of theimaging plane, and the reference position of the imaging range is areference position of the two-dimensional disposition of the pluralityof imaging elements.

A plurality of imaging elements disposed in two dimensions are used todetermine the reference position of the imaging position; and since theplurality of imaging elements disposed in two dimensions have regularityin terms of shape and outline, etc., positions can easily be specified.

The above object is accomplished by another unique structure of thepresent invention for an offset measuring mechanism for measuring offsetin a bonding apparatus that includes:

-   -   a position detection camera that detects the position of a part        to be bonded on a bonding working plane,    -   a bonding tool that is disposed with an offset from the position        detection camera, and    -   a moving means for moving the position detection camera and the        bonding tool as an integral unit on a plane parallel to the        bonding working plane; and    -   in the present invention, the offset measuring mechanism that        measure the above-described offset comprises:    -   a measurement reference member provided inside the position        detection camera, the measurement reference member being        disposed in a reference member disposition position that is        associated with a reference position of the imaging range within        the imaging plane of the position detection camera and that is        in a different plane from the imaging plane of the position        detection camera, and an image of the measurement reference        member disposed in the reference member disposition position        being projected toward the bonding working plane;    -   an offset measuring camera which is disposed on an opposite side        of the bonding working plane from the position detection camera        and the bonding tool and which faces the bonding working plane;    -   an imaging range measuring means which uses the moving means to        move the position detection camera into a measurement range of        the offset measuring camera and which determines the reference        position of the imaging range of the position detection camera        based upon measurement of the reference member disposition        position the measurement reference member by the offset        measuring camera;    -   a tool position measuring means which uses the moving means to        move the bonding tool into the measurement range of the offset        measuring camera and which measures a tool position of the        bonding tool with the offset measuring camera; and    -   an offset calculating means which calculates the offset based        upon the determined reference position of the imaging range and        a measured value of the tool position.

In the above structure, the measurement reference member is disposed ina reference member disposition position inside the position detectioncamera. Furthermore, an image of the member disposed in the referencemember disposition position is projected toward the bonding workingplane by the optical system of the position detection camera, and thereference member disposition position the measurement reference memberis measured from this projected image by the offset measuring camera,thus determining the reference position of the imaging range of theposition detection camera. Furthermore, the tool position of the bondingtool is measured by the offset measuring camera, and the offset iscalculated based upon these measured values.

In other words, the offset measuring camera is fixed with respect to thebonding apparatus. Accordingly, by way of measuring, for instance, theposition (the reference member disposition position) of the measurementreference member with respect to the reference point of the imagingplane with the use of the measurement reference axes or measurementreference origin as a reference and by measuring the tool position ofthe bonding tool, the offset can be determined based upon thesemeasurement results. Accordingly, the offset can be calculated withoutusing a reference member that is exposed to the outside and thus in adanger of contamination or damage, and offset measurements can beperformed in a stable fashion over a long period of time.

It is preferable that the object plane of the position detection cameraand the object plane of the offset measuring camera coincide. Here, theterm “object plane” refers to the object plane in an optical system, andit indicates the plane where (it is assumed that) the object beingobserved will be disposed (when the optical system is designed). By wayof disposing the object of observation on the object plane, observationwith the highest precision can be accomplished. With the structuredescribed above, the imaging plane of the position detection camera isprojected with good precision on the object plane; and since theprojected image is on the object plane of the offset measuring camera,this image is projected onto the imaging plane of the offset measuringcamera with good precision. Consequently, the reference position of theimaging range of the position detection camera can be easily measuredwithout using a special reference member that is exposed to the outside.

Furthermore, it is preferable that the offset measuring camera has anobject side telecentric optical system, because with such a camera,stable position measurements can be performed even if the position ofthe object plane of the position detection camera or the position of thebonding tool fluctuates.

Furthermore, it is preferable that the offset measuring mechanismfurther includes an offset measuring camera magnification calculatingmeans that: uses the moving means to move the bonding tool into themeasurement range of the offset measuring camera and further to move thebonding tool within the measurement range, moves the bonding toolfurther in the measurement range so as to measure an amount of movementof an image of the bonding tool on the imaging plane of the offsetmeasuring camera corresponding to the amount of movement, and calculatesmagnification of the offset measuring camera based upon an amount ofmovement of the bonding tool and an amount of movement of the image ofthe bonding tool.

With structure above, the actual magnification of the offset measuringcamera can be determined based upon the measurement of the actual amountof movement of the bonding tool, rather than the nominal magnificationof the offset measuring camera, so that the precision of the calculationof the offset can be improved.

It is also preferable that the offset measuring mechanism furtherincludes a position detection camera magnification calculating meansthat: uses the moving means to move the bonding tool into a measurementrange of the offset measuring camera, and calculates a magnification ofthe position detection camera based upon measurement of predetermineddimensions of the plurality of imaging elements by the offset measuringcamera.

It is additionally preferable that the offset measuring mechanismfurther includes a position detection camera magnification calculatingmeans that: uses the moving means to move the bonding tool into ameasurement range of the offset measuring camera, and calculates amagnification of the position detection camera based upon measurement ofpredetermined dimensions of the measurement reference member by theoffset measuring camera.

With the above structures, the actual magnification of the positiondetection camera can be determined based upon the measurement of theactual dimensions of the imaging elements or the actual dimensions ofthe measurement reference member, instead of the nominal magnificationof the position detection camera, so that the precision of thecalculation of the offset can be improved.

It is preferable that the offset measuring mechanism further includes anoffset measuring camera inclination calculating means that: uses themoving means to move the bonding tool into the measurement range of theoffset measuring camera and to further move the bonding tool within themeasurement range, measures the movement direction of an image of thebonding tool on the imaging plane of the offset measuring cameracorresponding to the movement relative to mutually perpendicularmeasurement reference axes on the imaging plane of the offset measuringcamera, and calculates the relative inclination between movementreference axes of the moving means and measurement reference axes of theoffset measuring camera based upon the movement direction of the bondingtool relative to mutually perpendicular movement reference axes of themoving means and the movement direction of an image of the bonding tool.

In this structure, the relative inclination between the movementreference axes of the moving means and the measurement reference axes ofthe offset measuring camera is determined based upon the measurement ofthe direction of the movement of the bonding tool that actually occursin the actual bonding environment. Accordingly, the precision of thecalculation of the offset can be improved.

It is additionally preferable that the offset measuring mechanismfurther includes a position detection camera inclination calculatingmeans that: uses the moving means to move the position detection camerainto the measurement range of the offset measuring camera, andcalculates the relative inclination of imaging reference axes of theposition detection camera and measurement reference axes of the offsetmeasuring camera based upon measurement of inclination of the elementdisposition axes relative to mutually perpendicular measurementreference axes in the imaging plane of the offset measuring camera.

In this structure, the relative inclination between the imagingreference axes of the position detection camera and the measurementreference axes of the offset measuring camera is determined based uponthe measurement of the inclination for the actually occurring elementdisposition axes of the imaging elements in the actual bondingenvironment, so that the precision of the calculation of the offset canbe improved. In this case, the actually measured inclination for theelement disposition axes of the imaging elements includes a component inwhich the element disposition axes of the imaging elements themselvesare inclined with respect to the measurement reference axes of theoffset measuring camera, and a component in which the imaging referenceaxes of the position detection camera themselves are twisted in theoptical path between the imaging plane and the object plane, so thatthis inclination indicates the so-called comprehensive inclination ofthe imaging reference axes for the position detection camera.

The above object is further accomplished by a sequential set of uniquesteps of the present invention for an offset measuring method in abonding apparatus that includes:

-   -   a position detection camera that detects the position of a part        to be bonded on a bonding working plane,    -   a bonding tool that is disposed with an offset from the position        detection camera,    -   a moving means for moving the position detection camera and the        bonding tool as an integral unit on a plane parallel to the        bonding working plane; and    -   an offset measuring camera which is disposed on the opposite        side of the bonding working plane from the position detection        camera and the bonding tool and which faces the bonding working        plane; and    -   in the present invention, the offset measuring method that        measures the above-described offset includes:    -   an imaging position measurement step fort moving, with a use of        the moving means, the position detection camera into the        measurement range of the offset measuring camera and measuring        the reference position of the imaging range in an imaging plane        of the position detection camera based upon observation of the        imaging plane of the position detection camera by the offset        measuring camera,    -   a tool position measurement step for moving, with a use of the        moving means, the bonding tool into the measurement range of the        offset measuring camera and measuring the tool position of the        bonding tool by the offset measuring camera, and    -   an offset calculation step for calculating the offset based upon        the measured value of the reference position of the imaging        range and the measured value of the tool position.

The above object is further accomplished by another sequential set ofunique steps of the present invention for an offset measuring method ina bonding apparatus that includes:

-   -   a position detection camera that detects the position of a part        to be bonded on a bonding working plane,    -   a bonding tool that is disposed with an offset from the position        detection camera,    -   a moving means for moving the position detection camera and the        bonding tool as an integral unit on a plane parallel to the        bonding working plane, and    -   a measurement reference member provided inside the position        detection camera, the measurement reference member being        disposed in a reference member disposition position that is        associated with a reference position of the imaging range within        the imaging plane of the position detection camera and that is        in a different plane from the imaging plane of the position        detection camera, and the image of the measurement reference        member disposed in the reference member disposition position        being projected toward the bonding working plane, and    -   an offset measuring camera which is disposed on the opposite        side of the bonding working plane from the position detection        camera and the bonding tool and which faces the bonding working        plane; and    -   in the present invention, the offset measuring method that        measures the above-described offset includes:    -   an imaging range measurement step for moving, with a use of the        moving means, the position detection camera into the measurement        range of the offset measuring camera and measuring the reference        position of the imaging range of the position detection camera        based upon the observation of the reference member disposition        position the measurement reference member by the offset        measuring camera,    -   a tool position measurement step for moving, with a use of the        moving means, the bonding tool into the measurement range of the        offset measuring camera and measuring the tool position of the        bonding tool by the offset measuring camera, and    -   an offset calculation step for calculating the offset based upon        the measured value of the reference position of the imaging        range and the measured value of the tool position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a bonding apparatus equipped with an offsetadjustment mechanism according to the embodiment of the presentinvention;

FIG. 2 is a partial perspective view of the bonding apparatus equippedwith the offset adjustment mechanism of the embodiment of the presentinvention, showing the manner of offset measurement in schematic terms;

FIG. 3 is a diagram showing the manner of detecting the imaging elementsof the position detection camera by the offset measuring camera in theembodiment of the present invention;

FIG. 4 is a diagram showing the manner of projecting the image of theimaging elements of the position detection camera onto the imagingelements of the offset measuring camera in the embodiment of the presentinvention;

FIG. 5 is a diagram showing the manner of detecting the tip end of thebonding tool by the offset measuring camera in the embodiment of thepresent invention;

FIG. 6 is a diagram showing the manner of projecting the tip end of thebonding tool onto the imaging elements of the offset measuring camera inthe embodiment of the present invention;

FIG. 7 is a flow chart of offset measurement in the embodiment of thepresent invention;

FIG. 8 is a diagram showing the manner of the image on the imagingelements of the offset measuring camera in offset measurement of theembodiment of the present invention;

FIG. 9 is a diagram showing the manner of detecting the referenceposition of the imaging range of the position detection camera by theoffset measuring camera is another embodiment of the present invention;

FIG. 10 is a diagram showing the manner of projecting the image of themeasurement reference member onto the imaging elements of the offsetmeasuring camera in another embodiment of the present invention;

FIG. 11 is a diagram showing the manner of determining the inclinationbetween the movement reference axes and the measurement reference axesin the embodiment of the present invention; and

FIG. 12 is a diagram showing the manner of determining the inclinationbetween the measurement reference axes and the disposition referenceaxes in the embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described in detail belowwith reference to the accompanying drawings.

In FIG. 1 is a block diagram of a bonding apparatus 10 equipped with anoffset adjustment mechanism. In the following description, a wirebonding apparatus will be described as a bonding apparatus; however, thepresent invention is applicable to a bonding apparatus that does not usewires. In other words, the present invention can be used in, forinstance, cases where, for example, a semiconductor device equipped withbumps and a lead frame are bonded by wireless bonding and where asemiconductor device and another part, e.g., another semiconductordevice, etc. are bonded by die bonding under accurate positioning.

In FIG. 1, the bonding apparatus 10 comprises a bonding head 12, amoving mechanism 14 which moves the bonding head in the horizontalplane, a conveying mechanism 16 which conveys lead frames, etc., anoffset measuring camera 18 which is used to measure the offset(described later), and a control block 20 which controls the respectiveconstituent elements overall.

A position detection camera 24 is attached to the bonding head 12 via acamera holder 22, and a bonding tool 28 is attached via a bonding arm26. The position detection camera 24 detects the positions of bondinglocations on the object of bonding; and the object plane of this cameraposition detection camera 24 is set at the surface of the object ofbonding. The bonding tool 28 is a tubular capillary which holds aslender wire that passes through this capillary. The bonding tool 28 canbe moved in the vertical direction by the bonding arm 26. Bonding energyis supplied to the bonding tool 28 from an ultrasonic transducer (notshown in the drawings).

The position detection camera 24 and bonding tool 28 are disposed withan offset relative to each other. These elements are movable in thehorizontal plane by the moving mechanism 14 as an integral unit with thebonding head 12 while this offset is maintained.

The conveying mechanism 16 mounts parts 30 that are to be bonded, suchas lead frames on which LSI chips are die-bonded, etc., on a carrier;and it conveys these elements into a bonding working region beneath thebonding tool 28.

The control block 20 has the function of operating control of therespective constituent elements and can be constructed using a commoncomputer. Besides the control of wire bonding for the parts 30 that areto be bonded, the control block 20 functions to calculate and correctthe offset between the position detection camera 24 and the bonding tool28.

For the purpose of executing offset calculation, the control block 20 iscomprised of: an imaging position measuring section 42 which determinesthe reference position of the imaging plane of the position detectioncamera 24, a tool position measuring section 44 which determines theposition of the bonding tool, an offset calculating section 46 whichcalculates and corrects the offset, a first magnification calculatingsection 48 which calculates the magnification of the offset measuringcamera 18, a second magnification calculating section 49 whichcalculates the magnification of the position detection camera 24, afirst inclination calculating section 50 which determines theinclination between the movement reference axes of the moving mechanism14 and the measurement reference axes of the offset measuring camera 18,a second inclination calculating section 52 which determines theinclination between the imaging reference axes of the position detectioncamera 24 and the measurement reference axes of the offset measuringcamera 18, and a moving mechanism control section 54 which controls themovement of the moving mechanism 14.

FIG. 2 is a partial perspective view of the bonding apparatus 10,showing the conditions of offset measurement in schematic terms. In FIG.2, the conveying mechanism is omitted, and the bonding working plane 60corresponding to the surface of the part that is to be bonded isindicated by two-dot chain lines. The conveying device may be retractedduring offset measurement; instead, a system can be used in which theposition detection camera 24 is disposed in such a position that thiscamera does not interfere with the conveying device, and the conveyingdevice is not retracted even during offset measurement.

The object plane of the position detection camera 24 is set so that thisobject plane coincides with the bonding working plane 60; and whenbonding work is performed, the bonding tool 28 is set so that the tipend of this bonding tool is lowered to the bonding working plane 60. Asshown in FIG. 2, the position detection camera 24 and bonding tool 28have an offset 62, and they are disposed on the same side of the bondingworking plane 60. The offset measuring camera 18 is, on the other hand,disposed on the opposite side of the bonding working plane 60.

The position detection camera 24 is an imaging camera, and it faces thebonding working plane. The position detection camera 24 includes (insidea cylindrical lens barrel) an imaging plane 72, on which a plurality ofimaging elements 70 are disposed in two dimensions, and an optical lens74, whose image plane is the imaging plane 72 and whose object plane isthe bonding working plane 60.

Here, the term “object plane” refers to the object plane in an opticalsystem, and it indicates the plane where (it is assumed that) the objectbeing observed will be disposed (when the optical system is designed).In other words, if a point light source is disposed on the object plane,the light emitted from this light source will be focused on the imagingplane as a point image with a size that satisfies the designspecifications of the optical system; and thus by way of disposing theobject of observation on the object plane, observation with the bestprecision is possible.

The optical lens 74 can be a single lens; however, it can be constructedfrom an optical system that combines a plurality of optical elementssuch as lenses and filters, etc. The optical lens 74 functions to forman image 78 of the plurality of imaging elements 70 (on the imagingplane 72) on the bonding working plane 60 via the light path 76.

The offset measuring camera 18 is installed separately from the positiondetection camera 24 and faces the bonding working plane 60. The objectplane of the offset measuring camera 18 is set on the bonding workingplane 60. The offset measuring camera 18 comprises (inside a cylindricallens barrel) an imaging plane 82, on which a plurality of imagingelements 80 disposed in two dimensions are installed, and an opticallens 84, whose image plane is the imaging plane 82 and whose objectplane is the bonding working plane 60.

The optical lens 84 can be a single lens, and it can be constructed froman optical system that combines a plurality of optical elements such aslenses and filters, etc. The optical lens 84 functions to project animage that is formed on the bonding working plane 60 onto the imagingplane 82 of the offset measuring camera 18 via the light path 86.

In the shown embodiment, the image 78 of the plurality of imagingelements 70 of the position detection camera 24 that is formed on thebonding working plane 60 is projected onto the imaging plane 82 of theoffset measuring camera 18 and detected by the imaging element 80.

FIG. 3 illustrates, in terms of the optical path, how the imagingelements of the position detection camera 24 are detected by the offsetmeasuring camera 18.

First, the bonding head 12 is moved by the moving mechanism, so that theposition detection camera 24 is moved into the visual field, i.e., themeasurement range, of the offset measuring camera 18. In this state, asshown FIG. 3, the optical path of the optical lens 74 of the positiondetection camera 24 is set so that the image plane is at the imagingplane 72 and so that the object plane is at the bonding working plane60. Accordingly, the image of the imaging elements 70 on the imagingplane 72 is focused on the bonding working plane 60 by the optical lens74 via the light path 76. On the other hand, the optical path of theoptical lens 84 of the offset measuring camera 18 is set so that theimage plane is at the imaging plane 82 and so that the object plane isat the bonding working plane. Accordingly, the image on the bondingworking plane 60 is projected onto the imaging elements 80 via the lightpath 86 of the optical lens 84. Thus, since the two cameras 24 and 18are disposed so that the object planes thereof of are coincide and thusare both at the bonding working plane 60, the image (70) of the imagingelements of the position detection camera 24 is detected by the imagingelements 80 of the offset measuring camera 18.

FIG. 4 shows how the image (70) of the imaging elements of the positiondetection camera 24 is projected onto the imaging elements 80 within theimaging plane 82 of the offset measuring camera 18.

FIG. 5 illustrates how the tip end of the bonding tool 28 is detected bythe offset measuring camera 18 in terms of the optical path.

First, the bonding head (12) is moved by the moving mechanism, so thatthe bonding tool 28 is moved into the visual field, i.e., themeasurement range, of the offset measuring camera 18, and the bondingarm is lowered so that the tip end of the bonding tool 28 reaches thebonding working plane 60. As described above, the optical path of theoptical lens 84 of the offset measuring camera 18 is set so that theimage plane is at the imaging plane 82, and so that the object plane isat the bonding working plane. Accordingly, the image of the tip end ofthe bonding tool 28 on the bonding working plane 60 is formed on theimaging elements 80 via the light path 86 of the optical lens 84. Thus,since the tip end of the bonding tool 28 is caused to coincide with theobject plane of the offset measuring camera 18, the image (28) of thetip end of the bonding tool can be detected by the imaging elements 80of the offset measuring camera 18.

FIG. 6 shows how the tip end of the bonding tool 28 is projected ontothe imaging elements 80 within the imaging plane 82 of the offsetmeasuring camera 18.

In the above, though the object plane of the optical lens 74 and theobject plane of the optical lens 84 coincide, it is possible to use anobject-side telecentric optical system instead of such an optical lens74 and optical lens 84.

The term “object-side telecentric lens” or “object-side telecentricoptical system” refers to an optical system in which the principal lightrays that are focused as an image pass through a focal point on the backside of the lens. Such optical systems have a broad tolerance range forpositional deviation in the direction facing the focal plane and areknown for the fact that the size of the image, i.e., the distance fromthe optical axis, does not vary even if the object position fluctuatesin cases where the object is illuminated by transmitted light that isparallel light. By way of using such an object-side telecentric opticalsystem, images are detected by the offset measuring camera 18 withalmost no variation in the size of the images (70 and 28) that are to bedetected, even if the relative positions of the position detectioncamera 24 and offset measuring camera 18 fluctuate with respect to thebonding working plane 60.

Next, the method to measure the offset between the position detectioncamera 24 and the bonding tool 28 using the offset measuring camera 18in the above-described structure will be described with reference FIG.7, which is a flow chart, and FIG. 8, which shows the conditions of theimage on the imaging elements 80 of the offset measuring camera 18.

First, the position detection camera 24 is moved into the measurementrange of the offset measuring camera 18 (S10). This movement isaccomplished by controlling the moving mechanism 14 by means of themoving mechanism control section 54 of the control block 20. In thisstate, the image (70) of the imaging elements within the imaging plane72 of the position detection camera 24 is projected as shown in FIG. 8onto the imaging elements 80 of the imaging plane 82 of the offsetmeasuring camera 18. The projected image is detected by the imagingelements 80, and the resulting data is input into the imaging positionmeasuring section 42 of the control block 20.

Next, the reference position of the imaging range of the positiondetection camera 24 is measured in the imaging position measuringsection 42 (S12). Since the imaging range of the position detectioncamera 24 constitutes the positions where the imaging elements 70 aredisposed in two dimensions, the center position, for example, of theimaging elements 70 disposed in two dimensions can be taken as thereference position of the imaging range. The reference position can bedetermined by a correspondence calculation such as an operation in whichsome other easily recognizable position of the imaging elements 70,e.g., the position of the lower left corner point, etc., is measured,and the center position of the imaging elements is calculated based uponthe overall dimensions of the imaging elements disposed in twodimensions, which are known beforehand, and the magnification of theposition detection camera 24.

In FIG. 8, the movement reference axes of the moving mechanism 14 aredesignated as X_(O) and Y_(O), the measurement reference axes of theoffset measuring camera 18 are designated as X_(M) and Y_(M), and theimaging reference axes of the imaging plane of the position detectioncamera 24 that is projected are designated as X_(C) and Y_(C). It isassumed that the disposition reference axes X_(D) and Y_(D) of theimaging elements in the imaging plane of the position detection camera24 coincide with the imaging reference axes X_(C) and Y_(C). Here, ifthe origin of the measurement reference axes of the offset measuringcamera 18 is designated as O_(M), and the origin of the dispositionreference axes for the image (70) of the imaging elements of theposition detection camera 24 that is projected is designated as O_(C),then the reference position of the position detection camera 24 for themeasurement reference axes X_(M) and Y_(M) can be measured by(O_(C)−O_(M)). The measured reference position of the position detectioncamera 24 is input into the offset calculating section 46 of the controlblock 20.

Next, the bonding tool 28 is moved into the measurement range of theoffset measuring camera 18 (S14). The moving mechanism 14 is controlledby the moving mechanism control section 54 so that the bonding tool 28is moved by a nominal offset L_(O) along the movement reference axisY_(O) of the moving mechanism 14. Here, the term “nominal offset L_(O)”refers to a nominal distance set between the bonding tool 18 and theposition detection camera using the position detection camera 24 as areference. In this state, the image (28) of the tip end of the bondingtool 28 is projected as shown in FIG. 8 onto the imaging elements 80 ofthe imaging plane 82 of the offset measuring camera 18. The projectedimage is detected by the imaging elements 80, and this data is inputinto the tool position measuring section 44 of the control block 20.

Next, in the tool position measuring section 44, the tool position ofthe bonding tool 28 is measured (S16). In FIG. 8, if O_(B) is taken asthe center point of the projected image (28) of the tip end of thebonding tool, then the tool position is measured for the measurementreference axes X_(M), Y_(M) by means of (O_(B)−O_(M)). The measured toolposition is input into the offset calculating section 46 of the controlblock 20.

The order of the steps S10 and S12 and the steps S14 and S16 can bereversed. In either case, the measurement results for the referenceposition of the imaging range in the position detection camera 24 andthe measurement results for the tool position are input into the offsetcalculating section 46, and the actual offset L is calculated based uponthese results (S18). The actual offset L can be calculated by convertingthe reference position (O_(C)−O_(M)) of the position detection camera 24for the measurement reference axes X_(M), Y_(M), the tool position(O_(B)−O_(M)) and the nominal offset L_(O) into values using themovement reference axes X_(O), Y_(O) as a reference.

The simplest case will be described in which it is assumed that, forinstance, the movement reference axes X_(O), Y_(O), the dispositionreference axes X_(D), Y_(D) and the movement reference axes X_(M), Y_(M)all coincide, the magnification of the position detection camera 24 is1×, and the magnification of the offset measuring camera 18 is also 1×.In this case, since all of the coordinate systems coincide, if(O_(C)−O_(M)), (O_(B)−O_(M)) and L_(O) are taken as vectors, then theoffset L expressed by these vectors is given by L_(O)+(O_(B)−O_(M)).From this, the offset correction (S20) is given byL−L_(O)=(O_(B)−O_(M)).

In actuality, in the case of (O_(C)−O_(M)), correction of theinclination of the imaging reference axes X_(C), Y_(C) with respect tothe measurement reference axes X_(M), Y_(M), the inclination of thedisposition reference axes X_(D), Y_(D) with respect to the imagingreference axes X_(C), Y_(C), the magnification of the position detectioncamera 24 and the magnification of the offset measuring camera 18 isnecessary; and in the case of (O_(B)−O_(M)), correction of theinclination of the measurement reference axes X_(M), Y_(M) with respectto the movement reference axes X_(O), Y_(O) and the magnification of theoffset measuring camera 18 is necessary. The calculation of theinclinations between these respective reference axes, and thecalculation of the magnifications, will be described later.

FIG. 9 illustrates, in terms of the optical path, how the referenceposition of the imaging range of the position detection camera 25 isdetected by the offset measuring camera 18 in another embodiment of thepresent invention.

As seen from FIG. 9, the position detection camera 25 includes ameasurement reference member 90 and a half-mirror 92. The measurementreference member 90 is disposed in a reference member dispositionposition which is associated with a reference position of the imagingrange within the imaging plane 72 of the position detection camera 25,e.g., the center position of the imaging elements 70 and which is on aplane that differs from the imaging plane 72 of the position detectioncamera 25. For example, the reference member disposition position is setso that the light path length from the imaging elements 70 to thehalf-mirror 92 is equal to the light path length from the measurementreference member 90 to the half-mirror 92. Furthermore, the image of themeasurement reference member 90 disposed in the reference memberdisposition position is projected toward the bonding working plane 60 bythe half-mirror 92 via the light path 94.

Since the optical path of the optical lens 84 of the offset measuringcamera 18 is set so that its image plane is at the imaging plane 82 andits object plane is at the bonding working plane as described above, theimage of the measurement reference member 90 that is projected onto thebonding working plane 60 is projected onto the imaging elements 80 viathe light path 96 of the optical lens 84.

FIG. 10 shows how the image (90) of the measurement reference member 90is projected onto the imaging elements 80 within the imaging plane 82 ofthe offset measuring camera 18.

The projected image (90) of the measurement reference member 90 is inputinto the imaging position measuring section 42 of the control block 20(see FIG. 1) and is converted into the reference position of the imagingrange of the position detection camera 24 based upon the correspondencebetween the measurement reference member 90 and the center position ofthe imaging elements.

Thus, even in cases where the image within the imaging plane of theposition detection camera is, for example, amorphous and the referenceposition of the imaging range of the position detection camera isdifficult to measure with accuracy in the case of the method illustratedin FIGS. 3 and 4, the reference position of the imaging range of theposition detection camera 24 can be accurately measured by detecting animage of the measurement reference member.

The actual magnification of the offset measuring camera 18 is measuredin the following manner: First, the bonding tool 28 is moved into themeasurement range of the offset measuring camera 18. This step can beaccomplished by the same procedure as in the case of S14 in FIG. 7. Inthis state, the image (28) of the tip end of the bonding tool isprojected as shown in FIG. 8 onto the imaging elements 80 of the imagingplane 8 of the offset measuring camera 18. Then, the bonding tool 28 isfurther moved a specified distance by the moving mechanism 14. Thisspecified distance is designated as d_(o). The amount of movement d_(i)of the image (28) of the bonding tool of the imaging elements 80 of theoffset measuring camera 18 corresponding to the above-described amountof movement is measured. These values are input into the firstmagnification calculating section 48 of the control block 20. In thefirst magnification calculating section 48, n₁=d₁/d_(O) is calculated;the obtained value is taken as the magnification of the offset measuringcamera 18 and is used for calculations in the offset calculating section46, etc.

The actual magnification of the position detection camera 24 is measuredin the following manner: First, the position detection camera 24 ismoved into the measurement range of the offset measuring camera 18. Thisstep can be accomplished by the same procedure as in the case of S10 inFIG. 7. In this state, the image (70) of the imaging elements 70 in theimaging plane 72 of the position detection camera 24 is projected asshown in FIG. 8 onto the imaging elements 80 of the imaging plane 82 ofthe offset measuring camera 18. The dimension of the image (70) of theimaging elements, e.g., the longitudinal dimension c₁, is measured bythe offset measuring camera 18. The actual longitudinal dimension c_(O)of the imagine elements 70 disposed in two dimensions is predeterminedand thus known in advance. The magnification n₁ of the offset measuringcamera 18 is calculated as described above. These values are input intothe second magnification calculating section 49 of the control block 20.In the second magnification calculating section 49, n₂=(c_(O)*n₁)/c₁ iscalculated; the obtained value is taken as the magnification of theposition detection camera 24 and is used for calculations by the offsetcalculating section 46, etc.

Furthermore, the actual magnification of the position detection camera24 can be measured using the measurement reference member 90 illustratedin FIG. 9. In this case, the position detection camera 24 is first movedinto the measurement range of the offset measuring camera 18. This stepcan be accomplished by the same procedure as in the case of S10 in FIG.7. In this state, the image (90) of the measurement reference member 90contained in the position detection camera 24 is projected onto theimaging elements 80 of the imaging plane 82 of the offset measuringcamera 18. The dimension, e.g., the diameter dimension b₁, of themeasurement reference member 90 is measured by the offset measuringcamera 18. The actual diameter dimension b_(O) of the measurementreference member 90 is predetermined and thus known in advance, and themagnification n₁ of the offset measuring camera 18 is also calculated asdescribed above. These values are input into the second magnificationcalculating section 49 of the control block 20. In the secondmagnification calculating section 49, n₂=(b_(O)*n₁)/b₁ is calculated;the obtained value is taken as the magnification of the positiondetection camera 24 and is used for calculations by the offsetcalculating section 46, etc.

FIG. 11 shows how the inclination between the movement reference axesX_(O), Y_(O) and the measurement reference axes X_(M), Y_(M) isdetermined.

First, the bonding tool 28 is moved into the measurement range of theoffset measuring camera 18. In this state, the image (28) of the tip endof the bonding tool 28 is projected as shown in FIG. 11 onto the imagingelements 80 of the imaging plane 82 of the offset measuring camera 18.This procedure is the same as the process of S14 in FIG. 7 or the sameas the first portion of the above-described process that determines themagnification. Next, the bonding tool 28 is moved in one direction,e.g., the direction of X_(O), of the movement reference axes. Thedirection of movement of the image (28) of the tip end of the bondingtool in this case is shown by broken lines in FIG. 11.

The bearing (direction) of this movement direction with respect to themeasurement reference axes X_(M), Y_(M) is measured and input into thefirst inclination calculating section 50 of the control block 20. In thefirst inclination calculating section 50, the bearing of the movementdirection is calculated, and the inclination between the movementreference axes X_(O), Y_(O) and measurement reference axes X_(M), Y_(M)is supplied as θ₁ for calculations by the offset calculating section 46,etc.

FIG. 12 shows how the inclination between the measurement reference axesX_(M), Y_(M) and the disposition reference axes X_(D), Y_(D) isdetermined.

In actuality, there is an inclination of the imaging reference axesX_(C), Y_(C) with respect to the measurement reference axes X_(M), Y_(M)and an inclination of the disposition reference axes X_(D), Y_(D) withrespect to the imaging reference axes X_(C), Y_(C); however, since thelatter inclination is known in advance, determination of the inclinationbetween the measurement reference axes X_(M), Y_(M) and the dispositionreference axes X_(D), Y_(D) is sufficient for the calculation of theoffset.

First, the position detection camera 24 is moved into the measurementrange of the offset measuring camera 18. This step can be accomplishedby the same procedure as in the case of S10 in FIG. 7. In this state,the image (70) of the imaging elements within the imaging plane 72 ofthe position detection camera 24 is projected as shown in FIG. 12 ontothe imaging elements 80 of the imaging plane 82 of the offset measuringcamera 18.

Here, the inclination of the disposition reference axes of the imagingelements is measured with respect to the measurement reference axesX_(M), Y_(M) and is input into the second inclination calculatingsection 52 of the control block 20. In the second inclinationcalculating section 52, the inclination angle is measured; and theinclination between the measurement reference axes X_(M), Y_(M) and thedisposition reference axes X_(D), Y_(D) is supplied θ₂ for calculationsby the offset calculating section 46, etc.

As seen from the above offset measuring mechanism and offset measuringmethod of the present invention, the bonding tool and the positiondetection camera are offset with reference to each other and such anoffset is measured in a stable fashion over a long period of time.

1. An offset measuring mechanism in a bonding apparatus that includes: aposition detection camera that detects the position of a part to bebonded on a bonding working plane, a bonding tool that is disposed withan offset from said position detection camera, and a moving means formoving said position detection camera and said bonding tool as anintegral unit on a plane parallel to said bonding working plane, whereinsaid offset measuring mechanism that measures said offset comprises: anoffset measuring camera which is disposed on an opposite side of saidbonding working plane from said position detection camera and saidbonding tool and which faces said bonding working plane; an imagingposition measuring means which uses said moving means to move saidposition detection camera into a measurement range of said offsetmeasuring camera and determines a reference position of an imaging rangein an imaging plane of said position detection camera based uponmeasurement of said imaging plane of said position detection camera bysaid offset measuring camera; a tool position measuring means which usessaid moving means to move said bonding tool into said measurement rangeof said offset measuring camera and measures a tool position of saidbonding tool with said offset measuring camera; and an offsetcalculating means which calculates said offset based upon a measuredvalue of said determined reference position of said imaging range and ameasured value of said tool position; and said position detection camerahas a plurality of imaging elements disposed in two dimensions indirections of mutually perpendicular element disposition axes which asassociated with mutually perpendicular imaging reference axes of saidimaging plane; and said reference position of said imaging range is areference position of said two-dimensional disposition of said pluralityof imaging elements.
 2. The offset measuring mechanism according toclaim 1, wherein an object plane of said position detection camera andan object plane of said offset measuring camera coincide.
 3. The offsetmeasuring mechanism according to claims 1, wherein said offset measuringcamera has an object side telecentric optical system.
 4. The offsetmeasuring mechanism according to claims 1, further comprising an offsetmeasuring camera magnification calculating means, wherein said offsetmeasuring camera magnification calculating means: uses said moving meansto move said bonding tool into said measurement range of said offsetmeasuring camera and to further move said bonding tool within saidmeasurement range so as to measure an amount of movement of an image ofsaid bonding tool on said imaging plane of said offset measuring cameracorresponding to said amount of movement; and calculates magnificationof said offset measuring camera based upon an amount of movement of saidbonding tool and an amount of movement of said image of said bondingtool.
 5. The offset measuring mechanism according to claim 1, furthercomprising a position detection camera magnification calculating means,wherein said position detection camera magnification calculating means:uses said moving means to move said bonding tool into a measurementrange of said offset measuring camera; and calculates a magnification ofsaid position detection camera based upon measurement of predetermineddimensions of said plurality of imaging elements by said offsetmeasuring camera.
 6. The offset measuring mechanism according to claims1, further comprising an offset measuring camera inclination calculatingmeans, wherein said offset measuring camera inclination calculatingmeans: uses said moving means to move said bonding tool into ameasurement range of said offset measuring camera and to further movesaid bonding tool within said measurement range; measures a movementdirection of an image of said bonding tool on said imaging plane of saidoffset measuring camera corresponding to said movement relative tomutually perpendicular measurement reference axes on said imaging planeof said offset measuring camera; and calculates a relative inclinationbetween movement reference axes of said moving means and measurementreference axes of said offset measuring camera based upon a movementdirection of said bonding tool relative to mutually perpendicularmovement reference axes of said moving means and a movement direction ofan image of said bonding tool.
 7. The offset measuring mechanismaccording to claim 1, further comprising a position detection camerainclination calculating means, wherein said position detection camerainclination calculating means: uses said moving means to move saidposition detection camera into a measurement range of said offsetmeasuring camera, and calculates a relative inclination of imagingreference axes of said position detection camera and measurementreference axes of said offset measuring camera based upon measurement ofinclination of said element disposition axes relative to mutuallyperpendicular measurement reference axes in said imaging plane of saidoffset measuring camera.
 8. An offset measuring mechanism in a bondingapparatus that includes: a position detection camera that detects theposition of a part to be bonded on a bonding working plane, a bondingtool that is disposed with an offset from said position detectioncamera, and a moving means for moving said position detection camera,and said bonding tool as an integral unit on a plane parallel to saidbonding working plane, wherein said offset measuring mechanism thatmeasures said offset comprises: an offset measuring camera which isdisposed on an opposite side of said bonding working plane from saidposition detection camera and said bonding tool and which faces saidbonding working plane; an imaging position measuring means which usessaid moving means to move said position detection camera into ameasurement range of said offset measuring camera and determines areference position of an imaging range in an imaging plane of saidposition detection camera based upon measurement of said imaging planeof said position detection camera by said offset measuring camera; atool position measuring means which uses said moving means to move saidbonding tool into said measurement range of said offset measuring cameraand measures a tool position of said bonding tool with said offsetmeasuring camera; and an offset calculating means which calculates saidoffset based upon a measured value of said determined reference positionof said imaging range and a measured value of said tool position; andfurther comprising an offset measuring camera inclination calculatedmeans, wherein said offset measuring camera inclination calculatedmeans: uses said moving means to move said bonding tool into ameasurement range of said offset measuring camera and to further movesaid bonding tool within said measurement range; measures a movementdirection of an image of said bonding tool on said imaging plane of saidoffset measuring camera corresponding to said movement relative tomutually perpendicular measurement reference axes on said imaging planeof said offset measuring camera; and calculates a relative inclinationbetween movement reference axes of said moving means and measurementreference axes of said offset measuring camera based upon a movementdirection of said bonding tool relative to mutually perpendicularmovement reference axes of said moving means and a movement direction ofan image of said bonding tool.
 9. An offset measuring method in abonding apparatus comprising: utilizing the offset measuring mechanismof claim 1 to perform the steps of; an imaging position measurement stepusing said moving means for moving said position detection camera into ameasurement range of said offset measuring camera and for measuring areference position of an imaging range in an imaging plane of saidposition detection camera while measuring said imaging plane of saidposition detection camera with said offset measuring camera, a toolposition step using said moving means for moving said bonding tool intosaid measurement range of said offset measuring camera and measuring atool position of said bonding tool with said offset measuring camera,and an offset calculation step for calculating said offset based upon ameasured value of said reference position of said imaging range by saidposition detection camera and a measured value of said tool position bysaid offset measuring camera.
 10. An offset measuring mechanism in abonding apparatus comprising: a position detection camera that detectsthe position of a part to be bonded on a bonding working plane, saidposition detection camera having a plurality of imaging elementsdisposed in two dimensions in directions of mutually perpendicularelement disposition axes which are associated with mutuallyperpendicular imaging reference axes of an imaging plane; a bonding toolthat is disposed with an offset from said position detection camera, amoving means for moving said position detection camera and said bondingtool as an integral unit on a plane parallel to said bonding workingplane, and an offset measuring camera which is disposed on an oppositeside of said bonding working plane from said position detection cameraand said bonding tool and which faces said bonding working plane; andwherein said offset measuring mechanism utilizes an offset measuringmethod comprising the steps of: an imaging position measurement stepusing said moving means for moving said position detection camera into ameasurement range of said offset measuring camera for measuring areference position of an imaging range in an imaging plane of saidposition detection camera while measuring said imaging plane of saidposition detection camera with said offset measuring camera, saidreference position of said imaging plane being a reference position ofsaid two dimensional disposition of said plurality of imaging elements;a tool position measuring step using said moving means for moving saidbonding tool into said measurement range of said offset measuring cameraand for measuring a tool position of said bonding tool with said offsetmeasuring camera; and an offset calculating step for calculating saidoffset based upon a measured value of said determined reference positionof said imaging range by said position detection camera and a measuredvalue of said tool position by said offset measuring camera.